exporter: explicitly error if annotation attached for non-existent pl…

…atform

Signed-off-by: Justin Chadwell <me@jedevc.com>

exporter/containerimage/annotations.go

@@ -60,6 +60,17 @@ func ParseAnnotations(data map[string][]byte) (AnnotationsGroup, map[string][]by
 	return ag, rest, nil
 }
 
+func (ag AnnotationsGroup) Platforms() []ocispecs.Platform {
+	var ps []ocispecs.Platform
+	for pk := range ag {
+		p, err := platforms.Parse(pk)
+		if err == nil {
+			ps = append(ps, p)
+		}
+	}
+	return ps
+}
+
 func (ag AnnotationsGroup) Platform(p *ocispecs.Platform) *Annotations {
 	res := &Annotations{
 		IndexDescriptor:    make(map[string]string),

exporter/containerimage/export.go

@@ -208,6 +208,15 @@ func (e *imageExporterInstance) Export(ctx context.Context, src *exporter.Source
 		return nil, err
 	}
 	opts.AddAnnotations(as)
+	for _, p := range opts.Annotations.Platforms() {
+		pk := platforms.Format(p)
+		if src.Refs == nil {
+			return nil, errors.Errorf("invalid annotation: no platform %s found in source", pk)
+		}
+		if _, ok := src.Refs[pk]; !ok {
+			return nil, errors.Errorf("invalid annotation: no platform %s found in source", pk)
+		}
+	}
 
 	ctx, done, err := leaseutil.WithLease(ctx, e.opt.LeaseManager, leaseutil.MakeTemporary)
 	if err != nil {

exporter/oci/export.go

@@ -10,6 +10,7 @@ import (
 
 	archiveexporter "github.com/containerd/containerd/images/archive"
 	"github.com/containerd/containerd/leases"
+	"github.com/containerd/containerd/platforms"
 	"github.com/docker/distribution/reference"
 	"github.com/moby/buildkit/cache"
 	cacheconfig "github.com/moby/buildkit/cache/config"
@@ -109,6 +110,15 @@ func (e *imageExporterInstance) Export(ctx context.Context, src *exporter.Source
 		return nil, err
 	}
 	opts.AddAnnotations(as)
+	for _, p := range opts.Annotations.Platforms() {
+		pk := platforms.Format(p)
+		if src.Refs == nil {
+			return nil, errors.Errorf("invalid annotation: no platform %s found in source", pk)
+		}
+		if _, ok := src.Refs[pk]; !ok {
+			return nil, errors.Errorf("invalid annotation: no platform %s found in source", pk)
+		}
+	}
 
 	ctx, done, err := leaseutil.WithLease(ctx, e.opt.LeaseManager, leaseutil.MakeTemporary)
 	if err != nil {